Forklift trucks and other material handling vehicles are designed to operate in congested areas, and these areas typically include limited visibility and pedestrian traffic. It may therefore be desirable to limit the travel speed of forklift trucks in many situations.
In a forklift truck powered by an internal combustion engine, the engine provides power to propel a passenger compartment and also provides power to a forklift carriage for lifting material on the forks. Likewise, electric forklift trucks typically have a common motor for propelling the passenger compartment and for operating the forklift carriage. Prior efforts to control travel speeds of forklift trucks (particularly on forklift trucks powered by internal combustion engines) have generally limited the maximum throttle position or adjusted an engine governor to control maximum engine revolutions per minute. Both of these methods are not particularly desirable because they limit the available power from the engine (or motor) under all circumstances, including limiting the amount of power available for lifting. These methods also provide inconsistent control of travel speed.